Boric Acid: Why It Works for Ant Control

Boric acid is commonly used as a slow-acting active ingredient in dust and bait formulations for ant control. “This goes back to the slow kill,” said Camille Landry, technical director at Full Scope Pest Control, Houston, Texas. “It's not a contact kill. We want the ants to ingest something and then bring it back to the colony and share it.”

This way, you’re not only eliminating worker ants with your control measures. The use of boric acid facilitates colony elimination, no matter how far away the nest is from a structure, said Landry. “We want that entire colony queen and the brood to be affected, so boric acid works really well,” she said.           

Boric acid combined with a food source or attractant becomes very palatable to ants, Landry said. “Workers are always foraging, looking for a consumable food,” she said. “The boric acid is ingested, but it is brought back to the colony, and it's going to be shared with all. And that slow kill works really well. Ants are very sensitive to random deaths in the workers, so this gives time for everybody to have eaten at the table, per say.”

Kathy Daw, owner/manager of Bob’s Pest Control, El Paso, Texas, said she uses boric acid when treating wall voids, which provides long-term residual control of the pests. “Because when I'm dusting the voids, it's hard to pinpoint where the ants are going to be when you just see them coming out of the outlets or wherever. I'll open up, for example, an outlet, and we'll dust in there and the dust will fall. I'd say 99 percent of the time, it takes care of whatever the issue is with the ants. It's just easier to use.”

However, Chris Brennan, owner of Brennan’s Pest Control, Oak Park, Ill., warned that not all species of ants respond to boric acid in his experience. “I’ve watched odorous house ants, pavement ants and carpenter ants skip boric acid granular baits for Advance granular,” he said.

It’s also important to keep in mind the slow-acting nature of boric acid. According to the Mallis Handbook of Pest Control, the toxicant takes from seven to 10 days to cause insect mortality.